Lithium Camphor initiated Anionic Polymerization of C_(60) and Styrene

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｃｅｎｔｙｅａｒｓ，ｔｈｅｐｏｌｙｍｅｒｉｃｍｏｄｉｆｉｃａｔｉｏｎｏｆｆｕｌｌｅｒｅｎｅｈａｓａｔｔｒａｃｔｅｄａｇｒｅａｔｉｎｔｅｒｅｓｔ［１］．Ｆｕｌｌｅｒｅｎｅａｎｄｉｔｓｄｅｒｉｖａｔｉｖｅｓｃａｎｂｅｄｉｒｅｃｔｌｙｉｎｃｏｒｐｏｒａｔｅｄｉｎｔｏａｖａｒｉｅｔｙｏｆｐｏｌｙｍｅｒｓｂｙｃｏｐｏｌｙｍｅｒｉｚａｔｉｏｎｏｒｇｒａｆｔｉｎｇ．Ｆｕｌｌｅｒｅｎｅ－ｂａｓｅｄｐｏｌｙｓｔｙｒｅｎｅａｎｄｉｔｓｄｅｒｉｖａｔｉｖｅｓｃａｎｂｅｐｒｅｐａｒｅｄｉ…     

PS-b-P (DMS-stat-VMS)嵌段聚合物的制备及性能

采用活性阴离子聚合方法,以仲丁基锂为引发剂,以苯乙烯、六甲基环三硅氧烷（D3）和2,4,6-三乙烯基-2,4,6-三甲基环三硅氧烷（V3）为反应单体,分步聚合制备了聚苯乙烯-b-聚（二甲基硅氧烷-stat-乙烯基甲基硅氧烷）[PS-b-P（DMS-stat-VMS）]嵌段聚合物.采用傅里叶变换红外光谱、氢核磁共振谱及凝胶渗透色谱对共聚物的化学结构、分子量及分子量分布进行了表征,并通过扫描电子显微镜、原子力显微镜及接触角等测试方法研究了共聚物各链段组分对共聚物形貌及表面亲疏水/油性的影响.结果表明,所制备的共聚物分子量分布较窄,由于各组分性能的差异而呈现出微相分离结构,同时该共聚物保留了PS-b-PDMS原有的表面性质,为设计结构多样性及性能优异的聚硅氧烷共聚物提供了新思路.     

通过阴离子型和阳离子型活性链的偶合反应合成甲基丙烯酸甲酯-四氢呋喃嵌段共聚物

两亲性或双亲水性嵌段共聚物在许多领域有重要的应用 ,如用作乳化剂 [1] 、结晶改性剂 [2～ 4 ] 和金属胶体模板物 [5] 等 .借助于活性聚合反应 (阴离子型、阳离子型、基团转移和自由基等 ) ,通过相继加入单体的方式 ,制备出了大量的嵌段共聚物 [6～ 9] ,但这种方法有一定局限性 .对于四氢呋喃与各种 (甲基 )丙烯酸酯的两亲性共聚物的合成 ,由于前者只能进行阳离子型开环聚合 ,而后者则只能进行阴离子聚合和自由基聚合 ,因此难以通过上述方法制得嵌段共聚物 .本文报道了通过 PTHF阳离子型活性链与 PMMA阴离子型活性链偶合反应制备 PMMA…     

Silazyl-Lithiums: A kind of new Initiators for the Anionic Non- equilibrium Ring-opening Polymerization of Octamethylcyclotetrasiloxane (D_4)

The anionic non-equilibrium polymerization of cyclosiloxane has mainly been focused on the polymerization of cyclosiloxanes initiated by organo-lithium, especially on the polymerization of hexamethylcyclotrisiloxane (D3)1-3. The polymerization of D4 initiated by the new hexamethyldi- silazyl-lithium (MMNLi) initiator was first studied in our lab4. The special characters of Si-N bond impart several advantages to the new silazyl-lithium initiator. The end group linked to Si-N bond could b…     

Synthesis of Telechelic Polystyrene by Radical Polymerization Using 1,4-Bis(p-tert-Butylphenylseleno-Methyl)benzene as a Photoiniferter

Abstract

1,4-Bis(p-tert-butylphenylselenomethyl) benzene was synthesized, and used as a bifunctional photoiniferter for the polymerization of styrene. Both the polymer yields and the number average of molecular weights (_n) of polymers increased with the polymerization. The polymerization of styrene by this iniferter permitted telechelic polystyrene containing arylseleno groups at both chain ends, and the degree of functionality was 1.9. The seleno groups of both chain ends of polystyrene were reduced quantitatively by tri-n-butyltin hydride. These seleno groups in polystyrene were also eliminated by treatment with hydrogen peroxide to give telechelic polystyrene with carbon-carbon double bond at both chain ends. Further, polystyrene with double bonds was converted to telechelic polystyrene carrying terminal functional groups as epoxy, hydroxy, and iodide group, respectively.

     

Kinetics and Mechanism of the Polymerization of Methyl Methacrylate in a Y(acac)3/n-BuMgCl System

Based on the kinetics equation proposed by T. Kagiya, the kinetic study on the polymerization of methyl methacrylate(MMA) by Y(acac)3/n-BuMgCl was carried out with a dilatometer. It was found that the rate of propagation is the first order with respect to the concentration of both active center and monomer. Thus, the equation of propagation rate can be described as Rp=Kp[c*][M]. In addition, the instantaneous chain initiation and single molecular termination were concluded for the present system. The activation energy is close to 32 kJ/mol. In the polymerization, n-BuMgCl acts not only as the cocatalyst, but also as chain transfer agent with cI=3.6×10-4.     

乙酸乙酯在D3F阴离子开环聚合中的促进作用

以硅醇钠为引发剂,乙酸乙酯(EA)为极性调节剂,在HAAKE转矩流变仪中合成了聚三氟丙基甲基硅氧烷(PMTFPS),探讨了三氟丙基甲基环三硅氧烷(D3F)聚合过程中EA的促进作用.结果表明,在120℃下,引发剂质量分数为2.74%,EA极性凋节剂浓度为0.30 mol/L,反应4 min时,PMTFPS的数均分子量((...     

Unusual Facial Selectivity in the Cycloaddition of Singlet Oxygen to a Simple Cyclic Diene(1)

Syntheses of 5-isopropyl-1,3-cyclohexadiene and syn-5-isopropyl-2,3-dioxabicyclo[2.2.2]octane, by routes that would allow completely diastereoselective introduction of deuterium labels, are described. The reaction of the isopropyl cyclohexadiene with singlet oxygen is shown to give an endoperoxide that is derived by preferential attack on the more sterically hindered face of the diene. A possible mechanistic explanation of this result is that the attack from the less hindered face leads to "ene" reaction rather than endoperoxide formation. However, this mechanism would require that the "ene" reaction and cycloaddition proceed via a common intermediate-presumably a perepoxide.     

聚合温度对聚氯乙烯树脂结构和性能的影响

采用凝胶渗透色谱法、¹³H NMR和DSC法测定了悬浮聚合PVC树脂的平均分子量、间规度、结晶度和玻璃化温度.结果表明:聚合温度下降,PVC的平均分子量上升,分子量的对数值与聚合温度的倒数成正比;PVC的间规度和结晶度均增大,在形成结晶的间规链段的最短长度(ξ_min)为6时,由间规度计算的结晶度理论值与测定值接近;分子量和结晶度增加的共同作用,使PVC的玻璃化转变温度上升.     

Effect of ketimide ligand for ethylene polymerization and ethylene/norbornene copolymerization catalyzed by (cyclopentadienyl)(ketimide)titanium complexes-MAO catalyst systems: Structural analysis for CpTiCl2(NCPh2)

Ligand effects on the catalytic activity [and norbornene (NBE) incorporation] for both ethylene polymerization and ethylene/NBE copolymerization using half-titanocenes (titanium half-sandwich complexes) containing ketimide ligand of type Cp′TiCl₂[NC(R¹)R²] [Cp′ = Cp (1), C⁵Me⁵ (Cp^∗, 2); R¹,R² = ^tBu,^tBu (a), ^tBu,Ph (b), Ph,Ph (c)]-methylaluminoxane (MAO) catalyst systems have been investigated. CpTiCl₂[NC(^tBu)Ph] (1b) CpTiCl₂(NCPh₂) (1c), and Cp^∗TiCl₂(NCPh₂) (2c) were prepared and identified; the structure of Cp^∗TiCl₂(NCPh₂) (2c) was determined by X-ray crystallography. The catalytic activity for ethylene polymerization increased in the order: 1a > 1b > 1c, suggesting that an electronic nature of the ketimide ligand affects the activity. However, molecular weight distributions for resultant (co)polymers prepared by 1b,c and by 2c-MAO catalyst systems were bi- or multi-modal, suggesting that the ketimide substituent plays a key role in order for these (co)polymerizations to proceed with single catalytically-active species. CpTiCl₂(NC^tBu₂) (1a) exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization.     

Anionic Polymerization Characteristics of the 1:1 Complex of n-Butylsodium and n-,s-Dibutylmagnesium (Sodium Tributylmagnesiate)

The behavior of isoprene and styrene polymerizations initiated by the complex of n-butylsodium and n-,s-dibutylmagnesium (sodium tributylmagnesiate) has been examined. The styrene-benzene system was found to yield stable active centers and polymers of predictable molecular weight and narrow molecular weight distributions. Isoprene, however, did not follow this behavior and yielded polydisperse material having molecular weights lower than those predicted on the basis that only n-butylsodium is capable of initiating chain growth. The polyisprene microstructure was found to consist of ～60% 3,4 and ～40% 1,4 units.     

1-(4-二甲基硅氢苯基)-1-苯乙烯/异戊二烯的活性阴离子交替共聚合调控研究

采用活性阴离子聚合方法研究了硅氢基功能化的1,1-二苯基乙烯(DPE)衍生物1-(4-二甲基硅氢苯基)-1-苯乙烯(DPE-SiH)与异戊二烯(Ip)在苯中的共聚反应,采用多种方法对序列分布、竞聚率和表观速率常数等进行测定.结果表明无调节剂下共聚物链中异戊二烯的插入量远多于DPE-SiH,DPE-SiH主要分布在聚合物...     

用Cadion-CPB光度法测定水中痕量阴离子表面活性剂

研究了用于直接测定水相中痕量阴离子表面活性剂的新体系。在ＮａＯＨ介质中,１－（４－硝基苯基）－３－［４－（苯基偶氮）苯基］－三氮烯（Ｃａｄｉｏｎ）与溴化十六烷基吡啶（ＣＰＢ）形成离子缔合物（Ｃａｄｉｏｎ－ＣＰＢ）,当加入阴离子表面活性剂（ＡＳ）时,ＡＳ能定量置换出离子缔合物中的Ｃａｄｉｏｎ,而使吸光度下降。阴离子表面活性剂十二烷基苯磺酸钠（ＤＢＯＳＯ３Ｎａ）、十二烷基磺酸钠（ＤＯＳＯ３Ｎａ）、十二烷基硫酸钠（ＤＳＯ４Ｎａ）的表观摩尔吸光系数εｍａｘ分别为２．７４×１０４、１．１１×１０４、１．５０×１０４Ｌ·ｍｏｌ－１·ｃｍ－１,服从比尔定律的范围分别为０～４．１８、０～６．５４、０～５．７７ｍｇ·Ｌ－１。方法操作简便,用于测定合成水样及环境水样中痕量阴离子表面活性剂,结果满意。     

Synthesis of Chlorotitanium(IV) Schiff‐Base Complexes and their Application to Styrene Polymerization

Summary: A [TiCl₂(salen)] complex and its derivatives with the formula [TiCl₂(L)] [L = salen(tBu), salen(di‐Me), salen(di‐tBu), salen(Me)] were synthesized in high yield by reacting the Schiff‐base ligands with TiCl₄. [TiCl₂{salen(tBu)}] and [TiCl₂{salen(di‐tBu)}] have been characterized by single‐crystal X‐ray diffraction. Styrene polymerizations carried out with [TiCl₂(salen)] and its derivatives co‐catalyzed by MAO yielded syndiotactic polystyrenes. The catalytic activity and syndiospecificity were dependent on the bulkiness of the ortho substituents in the aryl ring of ligand.

     

RE4[P1–x(C2)x]3 (RE = La–Nd): the Mixed Anionic Substructure Formed by Phosphorus and Carbon

The rare‐earth phosphide carbides RE₄[P_1–x(C₂)_x]₃ (RE = La, Ce, Pr, Nd) represent the first example of a mixed anionic substructure formed by phosphorus and carbon, being the first step toward the formation of the mixed inorganic P–C species. The peculiarities of the crystal structure, magnetic properties, XAS data, and quantum chemical calculation results confirm the ionic nature of the interaction between the rare‐earth cations RE and phosphorus anions, while complex interaction of π states of the C₂ anions and d (and/or f) states of the RE components is indicated. Thus, despite the extensive chemical analogy between the phosphide carbides and phosphide silicides, the atomic interactions stabilizing the structural motif are slightly different.     

Modification of Surface Reactivity by CO: Effects on Decomposition and Polymerization of Acetaldehyde on Ru(0001)

The adsorption and reaction of acetaldehyde on the clean and CO pre-covered Ru(0001) surfaces have been investigated using temperature programmed desorption method. On the clean Ru(0001) surface, the decomposition of acetaldehyde is the main reaction channel, with little polymerization occurring. However, on the CO pre-covered Ru(0001) surface, the decomposition of acetaldehyde is inhibited considerably with increasing CO coverage. Whereas, the polymerization occurs efficiently, especially at high CO coverage (θ_CO>0.5 ML), which is strongly CO coverage dependent. Combined with previous studies, the well-ordered hexagonal structure of CO layer formed on the Ru(0001) surface at high CO coverage that matches the configuration of paraldehyde is likely to be the origin of this remarkable phenomenon.     

Simulations for evaluation of kinetic methods in differential scanning calorimetry. Part 1. Application to single-peak methods: Freeman-Carroll, Ellerstein, Achar-Brindley-Sharp and multiple linear regression methods

In order to simplify the choice between different kinetic methods used in differential scanning calorimetry, an interesting way for testing kinetic treatments is proposed, using simulated thermoanalytical curves computed from given kinetic parameters. Applied to the study of a polymerization, we tested the Freeman-Carroll, Ellerstein, multiple linear regression (reaction-order model) and Achar-Brindley-Sharp methods. The test of the validity of the methods is performed using the LSM parameter that represents the fit between the mathematical treatment used in the kinetic model and known data. The study reveals the importance of the number of points used, i.e. the resolution, in the thermoanalytical curve recording, especially for the Freeman-Carroll and Ellerstein methods, there being an increase in the relative error on all the kinetic parameters when the number of points is decreased. Maximum relative errors are reported for the pre-exponential factor calculations. Evaluation of the enthalpy error on the determination of the kinetic parameters has been performed. Simulations obtained with various enthalpies indicate the necessity in such cases of computing a relative dimensionless LSM parameter (relative to the amplitude of the phenomena) in order to compare different thermal effects.     

1,3-Dipolar cycloaddition of diazoalkanes onto dimethyl 1-(formylamino)ethylenephosphonate: a new route to 1-aminocyclopropanephosphonic acids and 3-phosphorylated pyrazoles

Diazoalkanes regiospecifically react with dimethyl 1-(formylamino)ethylenephosphonate (1a) to afford 5-substituted dimethyl 3-(formylamino)-4,5-dihydro-3H-pyrazol-3-phosphonates 2 in high yields. Their thermal decomposition followed by hydrolysis provides a straightforward access to 2-substituted 1-aminocyclopropanephosphonic acids 4. Aromatization of 2 under acidic conditions leads to 3-phosphorylated pyrazoles 5.     

Poly(vinyl trimethylsilane) and block copolymers of vinyl trimethylsilane with isoprene: Anionic polymerization, morphology and gas transport properties

Poly(vinyl trimethylsilane) (PVTMS) and block copolymers of vinyl trimethylsilane with isoprene were synthesized by anionic polymerization and characterized. The synthesized pure PVTMS has properties similar to a reference material produced about two decades ago and can be used for thin film composite membrane formation. Even at low isoprene content the block copolymers have improved film forming properties compared to the pure PVTMS. However, the presence of the isoprene units in the block copolymers leads to a decrease of the gas permeability but does not affect the selectivity of the membranes (α(O₂/N₂) = 3.9).     

Kinetics of Complexation of Uranium with 2-(5-Bromo-2-Pyridylazo)-5-(Diethylamino) Phenol (Br-PADAP) in a 1:1 Water-Ethanol Medium

2-(5-Bromo-2-pyridylazo)-5-(diethylamino) phenol (Br-PADAP) forms a 1:1 complex with the uranyl ion in the presence of sulphosalicylic acid, which acts as stabilizer for this complex in the triethanol amine/perchloric acid buffer system. A change in the stoichiometry of the complex was seen at pH<5. Kinetic measurements were carried out using stopped-flow spectrophotometer in the presence of an excess concentration of U(VI) in the pH range 6.5 to 8. The dependence of the pseudo-first-order rate constant, k(obs), on the concentrations of U(VI), ligand and hydrogen ion showed that Br-PADAP reacts with UO₂(OH)⁺ to form an intermediate species (equilibrium constant = 1.28×10⁴mol.dm⁻³) that then rearranges (rate constant = 5.6×10⁻²s⁻¹) to form the product species. UO₂(OH)⁺ is present in equilibrium with the unreactive species UO₂(OH)₂, as well as with the unreactive sulfosalicylic acid complex.